My use of an angled end is probably influenced by the use of the Cocks & Bryant book as the first place I found making information. There are 3 blowpipes drawn in that excellent book and they all have angled ends. I didn't really think about it until Nick Leeming was helping me check some parts and asked me why the end was angled and I didn't have a good answer.Thinking about it now and with my engineer's hat on I would guess that the flap has to move through a smaller angle to open to a reasonable aparture than would be necessary on a right angles flap and it is possible that the force required to open it is smaller (this is a guess and may be nonsense<G>)

C & B must be taken cum grano salis. It is possibly in the words of the white knight - Something of my own invention.

I always presumed that the idea was that there would be an element of gravity closing the valve. With an angled seat the flap wants to fall onto the seat, whereas with a square face the valve could naturally sit a degree or 2 off closed, requiring bag pressure to achieve a seal. I think this argument is specious.

I learnt my pipemaking predominately with Colin Ross who always uses square ends although I can never remember any discussions on this point.

In my opinion, angled ends lead to difficulty of maintenance. It is certainly inconvenient to use a lathe centre on a piece with an angled face, and the valve flap is more difficult to construct.

If I have a set of pipes through my hands which will go out with my guarantee, I have always squared of the blowpipe seat. Of course I would not do this with a set which had historical significance. I have never found any problem with squared ends.

There is no practical advantage in an angled end. The 90 degree end suited the Reids and Dunn just fine, and I see no reason to 'improve' on their practice.I'm not even convinced by the gravity aspect, i.e having the leather hanging down. It makes not the slightest difference to the valves I make. I'd always advise anyone to insert the blowpipe correctly, i.e. with the leather hanging because in some instances it may make a difference, though with a carefully adjusted example it really doesn't seem to matter.